The effects of melatonin on the physical properties of bones and egg shells in the laying hen.

Taylor AC, Horvat-Gordon M, Moore A, Bartell PA - PLoS ONE (2013)

Bottom Line:
Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls.Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin.Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin.

Affiliation: Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, USA.

ABSTRACTLaying hens often experience unbalanced calcium utilization which can cause deficiencies in bone and egg mineralization. Because melatonin has been shown to affect bone mineralization in other animals, we examined whether treating hens with melatonin would affect eggshell thickness and improve skeletal performance, thereby reducing skeletal and egg shell defects. Birds were given a diet containing either low (30 µg/kg), medium (300 µg/kg), or high (3 mg/kg) concentrations of melatonin, or control feed through approximately one laying cycle. We examined the weight, length, and strength of egg, femur, tibia, and keel. Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls. Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin. Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin. Our data suggest that melatonin may affect the allocation of calcium to bone at the expense of egg shell mineralization.

pone-0055663-g008: Total egg weight was significantly greater in birds treated with low (63.69±0.37), medium (63.58±0.26), or high (63.04±0.34) concentrations of melatonin compared to those laid by control birds (61.67±0.36; p<0.001).Groups sharing a letter are not significantly different.

Mentions:
No significant differences were observed in any materials testing parameter for keels in any of the melatonin treatment groups (Table S1). One-way ANOVA determined that medullary bone ash weight was significantly affected by treatment (F(3,78) = 2.73, p<0.001), but multiple comparisons in Tukey's post-hoc test determined that there were no significant differences when comparing between birds treated with low (0.20 g±0.01), medium (0.16 g±0.00), or high (0.25 g±0.01) levels of melatonin, or controls (0.25 g±0.02; Fig. 7). Total egg weight was significantly greater in eggs laid by birds treated with low, medium, or high levels of melatonin, compared to eggs laid by control birds (F(3,805) = 6.92, p<0.001; Table 3; Fig. 8). Egg shell weight was also significantly greater in eggs laid by controls compared to those from birds treated with low, medium, or high levels of melatonin (F(3,805) = 870.89, p<0.001; Fig. 9). Egg content weight was significantly greater when laid by birds treated with low, medium, or high levels of melatonin compared to controls (F(3,805) = 41.01, p<0.001; Fig. 10).

pone-0055663-g008: Total egg weight was significantly greater in birds treated with low (63.69±0.37), medium (63.58±0.26), or high (63.04±0.34) concentrations of melatonin compared to those laid by control birds (61.67±0.36; p<0.001).Groups sharing a letter are not significantly different.

Mentions:
No significant differences were observed in any materials testing parameter for keels in any of the melatonin treatment groups (Table S1). One-way ANOVA determined that medullary bone ash weight was significantly affected by treatment (F(3,78) = 2.73, p<0.001), but multiple comparisons in Tukey's post-hoc test determined that there were no significant differences when comparing between birds treated with low (0.20 g±0.01), medium (0.16 g±0.00), or high (0.25 g±0.01) levels of melatonin, or controls (0.25 g±0.02; Fig. 7). Total egg weight was significantly greater in eggs laid by birds treated with low, medium, or high levels of melatonin, compared to eggs laid by control birds (F(3,805) = 6.92, p<0.001; Table 3; Fig. 8). Egg shell weight was also significantly greater in eggs laid by controls compared to those from birds treated with low, medium, or high levels of melatonin (F(3,805) = 870.89, p<0.001; Fig. 9). Egg content weight was significantly greater when laid by birds treated with low, medium, or high levels of melatonin compared to controls (F(3,805) = 41.01, p<0.001; Fig. 10).

Bottom Line:
Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls.Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin.Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin.

Affiliation:
Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, USA.

ABSTRACTLaying hens often experience unbalanced calcium utilization which can cause deficiencies in bone and egg mineralization. Because melatonin has been shown to affect bone mineralization in other animals, we examined whether treating hens with melatonin would affect eggshell thickness and improve skeletal performance, thereby reducing skeletal and egg shell defects. Birds were given a diet containing either low (30 µg/kg), medium (300 µg/kg), or high (3 mg/kg) concentrations of melatonin, or control feed through approximately one laying cycle. We examined the weight, length, and strength of egg, femur, tibia, and keel. Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls. Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin. Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin. Our data suggest that melatonin may affect the allocation of calcium to bone at the expense of egg shell mineralization.